Coral reefs are bleaching, an effect which can cause them to die. (When coral reefs undergo changes in temperature, light or nutrients, they expel the symbiotic algae that lives in their tissues, which makes them turn totally white. Some 90 percent of Australia's Great Barrier Reef has suffered bleaching.

Coral reefs are bleaching, an effect which can cause them to die. (When coral reefs undergo changes in temperature, light or nutrients, they expel the symbiotic algae that lives in their tissues, which